The invention relates to an arrangement for reducing the noise in an input signal formed by a speech signal mixed with noise.
Such an arrangement can be used to improve the listening comfort in telephone communication between two speakers located in a noisy environment. The microphone of each speaker produces a signal owing to acoustic noise which mixes with the speech signal during intersyllabic silences in the conversation and which may render it very difficult for the other speaker to hear what is said.
The listening comfort is already improved in communication systems which use automatic alternating control. In these systems a speech discriminator arrangement controls the switching circuits in such a manner that the connection between the microphone of one speaker and the receiver of the other speaker is not established until a speech signal is detected in the signal from the microphone. An arrangement of this type is described in, for example, the U.S. Pat. No. 4,243,837. But it should be noted that the automatic alternating control, which prevents that during the silent period one speaker hears the acoustic noise caught by the microphone of the other speaker, does not accomplish any improvement, during the conversation, for the speaker who listens to the other speaker who is speaking in a noisy environment; this speaker still hears acoustic noise superposed on the speech of the other speaker, particularly during the intersyllabic silences.